A non-singular terminal sliding mode control of the DC microgrid with constant power loads

Aiming at the problem that constant power load can easily cause DC microgrid bus voltage instability, a non-singular terminal sliding mode control strategy based on an extended state observer is proposed. First, according to the input-output precise feedback linearization theory, the BOOST circuit model is transformed into a Brunovsky standard form linear system, which solves the nonlinear problem caused by the constant power load. Then, a modified sliding mode surface is designed. The non-singular terminal sliding mode control law improves the system convergence speed and reduces system chattering. Considering the external disturbance and uncertainty of the system, an expanded state observer is designed to estimate it, and the estimated value is fed back to the non-singular terminal sliding mode control law, which further reduces the chattering of the system. Finally, based on Lyapunov theory, the stability analysis of the non-singular terminal sliding mode control law is performed. The proposed control strategy ensures that all error signals of the closed-loop system are consistent and ultimately bounded. Simulation results show that the proposed control strategy can effectively improve the response speed and robustness of DC microgrid systems with constant power loads.